This invention relates to the selective heating and cooling of the front and rear of a vehicle interior. More particularly, the present invention relates to a heating and cooling system that uses a three-fluid heat exchanger that joins the primary and secondary loops of the heating and cooling system. The three-fluid heat exchanger heats and cools the front of the vehicle and heats and chills the secondary loop that flows through a two fluid heat exchanger in the rear of the vehicle. The invention eliminates the typical rear evaporator and heater of traditional systems and replaces them with a less expensive two fluid heat exchanger.
Systems for selectively heating and cooling the front and rear of a vehicle are known. Typically, the rear air conditioning portion of these systems employs a separate evaporator and refrigerant lines that are connected to the primary loop or front air conditioning system of the vehicle. Having two separate systems increases the cost of the vehicle air conditioning system because of the need for a rear evaporator, additional refrigerant lines and valves, increased refrigerant charges and additional labor costs to install the separate system. One example of a dual evaporator system is described in U.S. Pat. No. 5,910,157.
There have been attempts to eliminate the duplication of components in systems used to heat and cool the front and rear of vehicles. In U.S. Pat. No. 5,904,052, (""052) a primary refrigerant system is employed to deliver decompressed refrigerant to a brine-refrigerant heat exchanger, which cools the brine. A pump pumps the cooled brine through a front air conditioning unit and a rear air conditioning unit. The system also employs the hot coolant water of the engine to control the temperature of the air that is provided to the vehicle. There is provided a common passage portion with switching valves through which both the hot coolant water and the brine flow into the air conditioning heat exchanger. One disadvantage of the system is its complexity. The system employs a brine-refrigerant heater and the engine coolant, plus air conditioning units that are separate from the brine-refrigerant heater. Due to this arrangement, the system requires a complex array of valves and piping, to heat and cool the vehicle.
A somewhat related system is described in U.S. Pat. No. 5,138,851. In this system, there is no concern for heating and cooling the front and rear of the vehicle; however, there is an effort to cool specific areas of the vehicle by using cooled water, which circulates through tubing located in various items of the vehicle. This patent discloses a closed loop air conditioning subsystem which has a motor which drives a compressor and which refrigerant fluid is compressed. The compressed fluid is passed into a condenser where the compressed fluid is cooled by dissipating its heat to the environment and from there the compressed fluid is released through an expansion valve into an evaporator. The second main component of the invention is a subsystem where working fluid is in heat exchange relationship with the evaporator of the first system whereby the working fluid is cooled in the evaporator and is thereafter sent by a pump or fan, driven by a suitable motor, into cooling members, such as cooling coils incorporated within the seat or other items within the vehicle. The evaporator of the traditional air conditioning system has an add on feature which includes conduits that are held in close proximity to the evaporator. In this way, the fluid within the conduits can be cooled by the evaporator and then pumped to the seats, steering wheel, etc. The difficulty with this system is that there is no teaching of heating the vehicle in the front and rear and in fact there is no teaching or suggestion how to cool the vehicle in the front and rear. Furthermore, the invention requires the use of an evaporator which adds cost and a fairly inefficient heat transfer mechanism associated with the evaporator.
The present invention overcomes the above problems associated with known attempts to effectively and efficiently heat and cool the front and rear of a vehicle. The present invention provides a vehicle climate control system with a separate control for the front and rear areas of the vehicle. The climate control system includes a three-fluid heat exchanger (refrigerant, coolant solution and air) having a first path with a first inlet and first outlet, and a second path with a second inlet and second outlet. The first path is adapted to communicate refrigerant between the first inlet and first outlet. The second path is adapted to communicate coolant between the second inlet and second outlet without the refrigerant and coolant being mixed. A refrigerant type loop or primary loop is provided. This loop includes a compressor and condenser interconnected by a refrigerant line with the refrigerant line being connected to the inlet and outlet of the first path such that the refrigerant passes through the three-fluid heat exchanger. The front area of the vehicle passenger compartment is cooled by this three-fluid heat exchanger and more particularly by the use of a fan blowing air across the three-fluid heat exchanger.
A secondary loop is provided having a dual fluid heat exchanger (coolant solution and air) and a coolant line connected to the inlet and the outlet of the second path such that the coolant flows through the three-fluid heat exchanger. The dual fluid heat exchanger is typically in the rear area of the vehicle passenger compartment. The coolant is cooled as it flows through the three-fluid heat exchanger by the refrigerant flowing through the three-fluid heat exchanger adjacent the coolant. The coolant is then passed through the dual fluid heat exchanger for cooling the rear passenger area of the vehicle. The secondary loop includes a simple fluid valve for diverting coolant from the dual fluid heat exchanger to control the cooling the rear of the vehicle.
In addition to the cooling system, the climate control system of the present invention includes a heating loop having a first heating conduit and a second valve for selectively connecting the secondary loop to the engine coolant system. The heating loop includes a second heating conduit and a third valve for selectively connecting the three-fluid heat exchanger to the vehicle engine coolant system. By manipulating the valves, the vehicle can be placed in an air conditioning mode wherein the valves prevent flow of fluid from the engine, and in a heating mode for the front and rear which utilizes the engine coolant and circulates it through the three-fluid heat exchanger and the dual fluid heat exchanger to heat and cool the front and the rear. In a rear-heating mode wherein the three-fluid heat exchanger is bypassed, only the rear heat exchanger is utilized.
In this invention, a rear-mounted heater and evaporator are eliminated. Additionally, the extra refrigerant, refrigerant lines and valving are not necessary. The system provides a very compact unit wherein the air conditioning circuit is substantially maintained within the vehicle engine compartment, the three-fluid heat exchanger is a small compact unit which can save instrument panel space and the typical components in the rear of the vehicle are eliminated saving space and cost.
The invention also allows for more flexibility in the placement of the heat exchangers. The heat exchangers can be placed in various locations in the vehicle to heat or cool specific areas for passenger comfort.